Recreating astronomical ices on earth
doi:10.1038/nindia.2017.37 Published online 27 February 2017
By simulating the frigid conditions of space between stars, astrophysicists have shed light on how complex molecules, such as ethanethiol, change from crystalline to amorphous and back1.It is this phase change that enables the icy molecules to lose or trap other molecules to form more complex molecules, a routine astronomical phenomenon in interstellar medium that mainly consist of gas and dust. This study offers potential for understanding how complex molecules form in icy space and has implications for the possibility of life on an Earth-like planet.
Grains in interstellar dust clouds host reactions that create hydrogen, water, methanol and even amino acids. But, it is difficult to simulate such extreme conditions on earth.
To recreate space-like conditions, scientists from Physical Research Laboratory, Ahmedabad and the National Synchrotron Radiation Research Centre, Taiwan vapour-deposited solid ethanethiol on a pre-cooled substrate at 4 degree Kelvin and then exposed it to higher temperatures in an ultra-high vacuum chamber.
When the thickness of ethanethiol ice was increased at 110 K, it changed from amorphous to crystalline. Increasing the temperature to 125 K changed the ice from crystalline to amorphous. When cooled from 125 K to 118 K, the amorphous ice became crystalline again, showing for the first time such phase changes in astronomical ices.
These results have implications for ethanethiol chemistry in the interstellar medium where thiols are known to take part in reactions that could lead to the formation of complex molecules in space, the researchers say.
1. Pavithraa, S. et al. Qualitative observation of reversible phase change in astrochemical ethanethiol ices using infrared spectroscopy. Spectrochim. Acta. Mol. Biomol. Spectros.178,166-170 (2017)